I am an extremely picky eater - don't like sauces or fancy foods, don't eat seafood or past dishes, don't like veggies. Extremely picky!
One of my biggest concerns, when we did our first cruise, was the food and how fancy it would be. But I really liked it. I picked badly at one restaurant (Parrot Cay) and, because I couldn't decide, our server brought me two meals and I didn't like either one (should have stuck with plain chicken or steak) but I didn't go hungry at all. And, on the last night, I ordered plain steak because I wanted to play it safe - one of our table mates ordered the duck dish (which I now understand is gone from the menu) and it looked so delicious, I had real food envy - he very kindly offered me some of his and I ate it all. It was unbelievably good - and I made a pact right there and then to try and be more adventurous when ordering.
Anyhow, back to your original question, there are plainer dishes available at all the restaurants and, with all the other options for eating, you definitely will not go hungry.